Bustin’ the riddims -- U.K.-style

British MCs have been slow to cross over to the American hip-hop nation, which hasn’t exactly been open to their epic collisions of stuttering bass lines, Jamaican dancehall riddims and sometimes impenetrable accents.

That’s unfortunate but hardly surprising, even for such forward-lookers as Sri Lankan rapper M.I.A. and the grime prodigy Dizzee Rascal. U.S. chart action is far quicker to follow predictability than progress.

So it was an encouraging scene Saturday at the Henry Fonda Music Box Theater, with a full house and scalpers outside charging triple for the night’s hot ticket, a blast of U.K. hip-hop from the Streets and the fast-rising Lady Sovereign.

Both are reaching to take the sound a step beyond the raw minimalism of early grime, but Lady Sov might be the first, best chance to make that impossible crossover, now that Jay-Z himself has signed her to Island Def Jam Records. She stepped onstage to the anxious beats of “Ch Ching,” looking like a diminutive boxer ready for a bout.

Sovereign paced the stage with a nervous, bratty charm, poking fun at herself and everything else. But the 20-year-old is no wannabe “Feminem” bowing to the commercial imperative of the moment. A new song, “Love Me or Hate Me,” was defiant and happily profane, with computer burps and beats and middle fingers to and from the crowd. Don’t look for it on the radio.

As her bassist and DJ rattled the dance floor with heavy beats and rhythms, Sovereign had clearly progressed by miles just since her appearance at Cinespace in December. The sound was bigger, her raps sharper, her ideas more musical.

Sound problems meant she couldn’t hear herself, but after a few stops and starts and complaints to an unseen sound man, she dived in anyway. Sovereign was the opening act here, so her set was over after barely 30 minutes. Which was a small tragedy.

Headlining was Mike Skinner, a.k.a. the Streets, among the first of his generation of U.K. rappers to reach U.S. ears with his 2002 debut, the acclaimed “Original Pirate Material.” As always, his delivery was less rapping than anxious chatter, words cluttered and tumbling forward, the occasional sung melody slipped into his rhymes.

Backed by a three-piece band and a vocalist sideman, Skinner started his 75-minute set with the soul-funk of “Pranging Out,” from his new album, “The Hardest Way to Make an Easy Living.” The new record has him contemplating the downside of fame and fortune, getting drunk and sexual performance, and the wisdom of not lying to chicks: “If you don’t tell a lie to her, you don’t have to remember anything.”

At his best, Skinner’s wiseguy one-liners were dynamic and sharp-witted, fired off typically half-cocked and half-bored. On the ska-flavored “Don’t Mug Yourself,” he led the crowd to bounce as one. But elsewhere, the man had gone a little tropical, a little romantic, a little soft.

Performing on a stage decorated with a warm silhouette of palm trees, Skinner spent too much of his set as Carnival Cruise lover man. Still, by the end, his fans were elated, cheering loudly for an encore. His core followers are still true believers, but blunting the edge of his startling early work hardly seems the way into the U.S. hip-hop nation.